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1.
Copper(II) and Zinc(II) Complexes of Conformationally Constrained Polyazamacrocycles as Efficient Catalysts for RNA Model Substrate Cleavage in Aqueous Solution at Physiological pH
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Daniel Bím Dr. Eva Svobodová Václav Eigner Dr. Lubomír Rulíšek Prof. Jana Hodačová 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10426-10437
As part of a quest for efficient artificial catalysts of RNA phosphodiester bond cleavage, conformationally constrained mono‐ and bis‐polyazamacrocycles in which tri‐ or tetraazaalkane chains link the ortho positions of a benzene ring were synthesized. The catalytic activities of mono‐ and dinuclear copper(II) and zinc(II) complexes of these polyazamacrocycles towards cleavage of the P?O bond in 2‐hydroxypropyl‐4‐nitrophenylphosphate (HPNP) in aqueous solution at pH 7 have been determined. Only the complexes of the ligands incorporating three nitrogen atoms in a macrocycle proved to be capable of efficiently catalyzing HPNP transesterification. The dinuclear complexes were found to be approximately twice as efficient as their mononuclear counterparts, and exhibited Michaelis–Menten saturation kinetics with calculated rate constants of kcat≈10?4 s?1. By means of quantum chemical calculations (DFT/COSMO‐RS), several plausible reaction coordinates were described. By correlating the calculated barriers with the experimental kinetic data, two possible reaction scenarios were revealed, with activation free energies of 20–25 kcal mol?1. 相似文献
2.
Bis(N‐Confused Porphyrin) as a Semirigid Receptor with a Chirality Memory: A Two‐Way Host Enantiomerization through Point‐to‐Axial Chirality Transfer
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Prof. Piotr J. Chmielewski Dr. Marta Siczek Prof. Marcin Stępień 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2547-2559
The adduct formation of protonated bis(N‐confused porphyrin) (BNCP, 3,3′‐bis(meso‐tetratolyl‐2‐aza‐21‐carbaporphyrin) with chiral anions, carboxylic acids, and alcohols was studied in solution by means of 1H NMR and circular dichroism (CD) spectroscopic analysis and DFT methods. The addition of enantiopure guests to the acidified BNCP resulted in optical activity that vanished after neutralization. Pairs of the 1H NMR‐distinguishable diastereomers were formed when enantiopure guests were applied, although a single form was observed upon the addition of the racemic mixtures in each case. Unidirectional configuration change that led to diastereomeric excess was observed in several instances. Such an excess was memorized by metalation of the adducts with AgBF4, thus resulting in optically active silver(III) complexes of BNCP with some enantiomeric excess. Absolute configurations of BNCP cations and bis(zinc) and bis(silver(III)) complexes were determined on the basis of time‐dependent (TD)‐DFT calculations of their CD spectra. It was shown that some of the chiral carboxylates induced opposite directions of enantiomerization of di‐ and tetracations or di‐/tetracation and bis(zinc) complexes. The source of the optical activity of the equimolar diastereomeric mixture of adducts is discussed. 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(40):12465-12469
The reaction of bis(η5:η1‐pentafulvene)titanium complexes with an allylidenephosphorylide Ph3P=C(H)‐ C(H)=CH2 leads to binuclear zigzag hexapentaene titanium complexes ( Ti2a , Ti2b ). The formation of the central C6H4 unit can be described as a spontaneous double C−H bond activation process, leading to an R3P=C=C=CH2 intermediate, as a synthon for a titanabutatriene fragment [(CpR)2Ti=C=C=CH2] (R: 2‐adamantyl, CH(p‐tol)2). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single‐crystal X‐ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations. 相似文献
4.
Molecular Calcium Hydride: Dicalcium Trihydride Cation Stabilized by a Neutral NNNN‐Type Macrocyclic Ligand
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Valeri Leich Dr. Thomas P. Spaniol Prof. Dr. Laurent Maron Prof. Dr. Jun Okuda 《Angewandte Chemie (International ed. in English)》2016,55(15):4794-4797
Hydrogenolysis of bis(triphenylsilyl)calcium containing the neutral NNNN‐type macrocyclic amine ligand Me4TACD [Ca(Me4TACD)(SiPh3)2] ( 2 ), gave the cationic dinuclear calcium hydride [Ca2H3(Me4TACD)2](SiPh3) ( 3 ), characterized by NMR spectroscopy, single‐crystal X‐ray analysis, and DFT calculations. Compound 3 reacted with deuterium to give the deuteride [D3]‐ 3 . 相似文献
5.
Hydro‐Alumination: Synthesis, Structure, and Properties of 1‐Methyl‐ cis ‐1‐azonia‐5‐alabicyclo[3.3.0]octane and of the Alan‐triallylamine Adduct The alan‐N‐methyl‐diallylamine adduct ( I ) was obtained by the reaction of N,N‐diallyl‐methyl‐ammoniumchloride with LiAlH4. Subsequently the reaction product was transformed by intramolecular hydro‐alumination reaction into bis(1‐methyl‐cis‐1‐azonia‐5‐alabicyclo[3.3.0]octane) ( II ). In contrast to I , the bis(alan‐triallylamine) adduct ( III ) does not undergo an analogous hydro‐alumination reaction. The compounds I , II and III were characterized by MS, IR, 1H‐, 13C‐ and 27Al‐NMR spectroscopy, and the X‐ray structures of II and III are reported and discussed. 相似文献
6.
Yun Xiong Shenglai Yao Robert Müller Martin Kaupp Matthias Driess 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(35):10392-10395
The synthesis and characterization of the first bis‐N‐heterocyclic carbene stabilized monomeric silicon disulfide (bis‐NHC)SiS2 2 (bis‐NHC=H2C[{NC(H)C(H)N(Dipp)}C:]2, Dipp=2,6‐iPr2C6H3) is reported. Compound 2 is prepared in 89 % yield from the reaction of the zero‐valent silicon complex (′silylone′) 1 [(bis‐NHC)Si] with elemental sulfur. Compound 2 can react with GaCl3 in acetonitrile to give the corresponding (bis‐NHC)Si(S)S→GaCl3 Lewis acid–base adduct 3 in 91 % yield. Compound 3 is also accessible through the reaction of the unprecedented silylone‐GaCl3 adduct [(bis‐NHC)Si→GaCl3] 4 with elemental sulfur. Compounds 2 , 3 , and 4 could be isolated and characterized by elemental analyses, HR‐MS, IR, 13C‐ and 29Si‐NMR spectroscopy. The structures of 3 and 4 could be determined by single‐crystal X‐ray diffraction analyses. DFT‐derived bonding analyses of 2 and 3 exhibited highly polar Si S bonds with moderate pπ–pπ bonding character. 相似文献
7.
The gas‐phase internal elimination (Ei) reaction of ethyl xanthate (CH3‐CH2‐S‐CS‐O‐CH3) has been investigated by means of Hartree–Fock, second‐order Møller–Plesset, and density functional theory (DFT) using the Becke three‐parameter Lee–Yang–Parr (B3LYP) functional and the modified Perdew–Wang one‐parameter model for kinetics (MPW1K). Considerable differences between the ground‐ and transition‐state geometries and the calculated activation energies are observed from one approach to the other, which justifies first a careful calibration of the methods against the results of benchmark CCSD(T) calculations. Compared with these, DFT calculations along with the MPW1K functional are found to be an appropriate choice for describing the Ei reaction of xanthate precursors. The precursor conformation and the transition states involved in the internal conversion of xanthate precursors of cyano derivatives of ethylene, and of cis‐ and trans‐stilbene, are then characterized in detail by means of this functional. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 2023–2031, 2003 相似文献
8.
Dr. Ramachandran Azhakar Dr. Rajendra S. Ghadwal Prof. Dr. Herbert W. Roesky Prof. Dr. Ricardo A. Mata Hilke Wolf Regine Herbst‐Irmer Prof. Dr. Dietmar Stalke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3715-3720
Three‐ and five‐membered rings that bear the (Si‐C‐S ) and (Si‐C‐C‐C‐S ) unit have been synthesized by the reactions of L SiCl ( 1 ; L =PhC(NtBu)2) and L′ Si ( 2 ; L′ =CH{(C?CH2)(CMe)(2,6‐iPr2C6H3N)2}) with the thioketone 4,4′‐bis(dimethylamino)thiobenzophenone. Treatment of 4,4′‐bis(dimethylamino)thiobenzophenone with L SiCl at room temperature furnished the [1+2]‐cycloaddition product silathiacyclopropane 3 . However, reaction of 4,4′‐bis(dimethylamino)thiobenzophenone with L′ Si at low temperature afforded a [1+4]‐cycloaddition to yield the five‐membered ring product 4 . Compounds 3 and 4 were characterized by NMR spectroscopy, EIMS, and elemental analysis. The molecular structures of 3 and 4 were unambiguously established by single‐crystal X‐ray structural analysis. The room‐temperature reaction of 4,4′‐bis(dimethylamino)thiobenzophenone with L′ Si resulted in products 4 and 5 , in which 4 is the dearomatized product and 5 is formed under the 1,3‐migration of a hydrogen atom from the aromatic phenyl ring to the carbon atom of the C? S unit. Furthermore, the optimized structures of probable products were investigated by using DFT calculations. 相似文献
9.
Carlo Carlini Alessandro Macinai Francesco Masi Anna Maria Raspolli Galletti Roberto Santi Glauco Sbrana Anna Sommazzi 《Journal of polymer science. Part A, Polymer chemistry》2004,42(10):2534-2542
The homopolymerization of ethylene by using different catalytic systems based on dinitro‐substituted bis(salicylaldiminate)nickel(II) precursors such as bis[3,5‐dinitro‐N(2,6‐diisopropylphenyl)]nickel(II) and bis[3,5‐dinitro‐N(phenyl)]nickel(II) in combination with organoaluminum compounds was investigated. In particular, the catalytic performances were studied as a function of the main reaction parameters, such as temperature, pressure, Al/Ni molar ratio, and duration. Methylaluminoxane resulted in the best co‐catalyst. Activities up to 200 kg polyethylene/(mol Ni × h) to give a linear high‐molecular‐weight polymer were achieved. The influence of the bulkiness of the substituents on the N‐aryl group of the aldimine ligand was also checked; it resulted in a determinant for catalytic activity rather than for polymer characteristics. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2534–2542, 2004 相似文献
10.
Quantum‐chemical analyses of aromaticity,UV spectra,and NMR chemical shifts in plumbacyclopentadienylidenes stabilized by Lewis bases
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Toshiaki Kawamura Minori Abe Masaichi Saito Masahiko Hada 《Journal of computational chemistry》2014,35(11):847-853
We carried out a series of zeroth‐order regular approximation (ZORA)‐density functional theory (DFT) and ZORA‐time‐dependent (TD)‐DFT calculations for molecular geometries, NMR chemical shifts, nucleus‐independent chemical shifts (NICS), and electronic transition energies of plumbacyclopentadienylidenes stabilized by several Lewis bases, (Ph)2(tBuMe2Si)2C4PbL1L2 (L1, L2 = tetrahydrofuran, Pyridine, N‐heterocyclic carbene), and their model molecules. We mainly discussed the Lewis‐base effect on the aromaticity of these complexes. The NICS was used to examine the aromaticity. The NICS values showed that the aromaticity of these complexes increases when the donation from the Lewis bases to Pb becomes large. This trend seems to be reasonable when the 4n‐Huckel rule is applied to the fractional π‐electron number. The calculated 13C‐ and 207Pb‐NMR chemical shifts and the calculated UV transition energies reasonably reproduced the experimental trends. We found a specific relationship between the 13C‐NMR chemical shifts and the transition energies. As we expected, the relativistic effect was essential to reproduce a trend not only in the 207Pb‐NMR chemical shifts and J[Pb‐C] but also in the 13C‐NMR chemical shifts of carbons adjacent to the lead atom. © 2014 Wiley Periodicals, Inc. 相似文献
11.
Essential Factors for Control of the Equilibrium in the Reversible Rearrangement of M3N@Ih‐C80 Fulleropyrrolidines: Exohedral Functional Groups versus Endohedral Metal Clusters
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Safwan Aroua Marc Garcia‐Borràs Dr. Sílvia Osuna Dr. Yoko Yamakoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):14032-14039
The effects of exohedral moieties and endohedral metal clusters on the isomerization of M3N@Ih‐C80 products from the Prato reaction through [1,5]‐sigmatropic rearrangement were systematically investigated by using three types of fulleropyrrolidine derivatives and four different endohedral metal clusters. As a result, all types of derivatives provided the same ratios of the isomers for a given trimetallic nitride template (TNT) as the thermodynamic products, thus indicating that the size of the endohedral metal clusters inside C80 was the single essential factor in determining the equilibrium between the [6,6]‐isomer (kinetic product) and the [5,6]‐isomer. In all the derivatives, the [6,6]‐ and [5,6]‐Prato adducts with larger metal clusters, such as Y3N and Gd3N, were equally stable, which is in good agreement with DFT calculations. The reaction rate of the rearrangement was dependent on both the substituent of exohedral functional groups and the endohedral metal‐cluster size. Further DFT calculations and 13C NMR spectroscopic studies were employed to rationalize the equilibrium in the rearrangement between the [6,6]‐ and [5,6]‐fulleropyrrolidines. 相似文献
12.
A Bis‐Sulfonyl O,C,O Aryl Pincer Ligand and its Tin(II) Complex: Synthesis,Structural Studies,and DFT Calculations
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Mohammad El Ezzi Romaric Lenk Dr. David Madec Dr. Jean‐Marc Sotiropoulos Sonia Mallet‐Ladeira Dr. Annie Castel 《Angewandte Chemie (International ed. in English)》2015,54(3):805-808
The efficiency of the deprotonated aryl bis‐sulfone [2,6‐{(p‐tolyl)SO2}2C6H3]? as an O,C,O‐coordinating pincer‐type ligand was described. The bis‐sulfone precursor was synthesized using a straightforward palladium‐catalyzed cross‐coupling reaction. As a result of directed ortho metalation (DoM) through sulfonyl groups, a selective lithiation of the aryl group was achieved and the corresponding carbanion was isolated and its structure determined by single‐crystal X‐ray diffraction analysis. A heteroleptic tin(II) complex has been prepared by a nucleophilic substitution reaction. Crystallographic analysis and DFT calculations indicate that the bis‐sulfonyl moiety acts as a new O,C,O‐coordinating pincer‐type ligand with intramolecular S?O coordination to a tin(II) center. The cis form with the two nonbonded oxygen atoms of the sulfonyl groups on the same side is preferentially obtained. 相似文献
13.
Synthesis and Theoretical Investigation of a 1,8‐Bis(bis(diisopropylamino)cyclopropeniminyl)naphthalene Proton Sponge Derivative
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Lee Belding Prof. Travis Dudding 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):1032-1037
We report herein the synthesis and characterization of a new proton sponge derivative, 1,8‐bis(bis(diisopropylamino)cyclopropeniminyl)naphthalene 4 (DACN), as well as its bis‐protonated counterpart 6 . A crystal structure of 6 is presented, along with variable temperature 1H NMR data on the BF4? salt ( 6?BF4 ). DFT calculations were performed to investigate the structure of the monoprotonated species 7 and to gain insight into the structural and electronic nature of all three species. The proton affinity (PA) of 4 , calculated at the B3LYP/6‐311G++(d,p)//B3LYP/6‐31G(d,p) level, taking into account thermal corrections from the B3LYP/6‐31G(d,p) method, was 282.3 kcal mol?1, while its pKa was estimated at 27.0. NICS calculations were performed to examine the changes in aromaticity within these systems upon each successive protonation. Lastly, homodesmotic reaction schemes were used in order to estimate the factors contributing to the strong PA predicted for 4 . 相似文献
14.
On the Reaction Mechanism of the Complete Intermolecular O2 Transfer between Mononuclear Nickel and Manganese Complexes with Macrocyclic Ligands
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Dr. Jhon Zapata‐Rivera Prof. Rosa Caballol Dr. Carmen J. Calzado Dr. Dimitrios G. Liakos Prof. Frank Neese 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13296-13304
The recently described intermolecular O2 transfer between the side‐on Ni‐O2 complex [(12‐TMC)Ni‐O2]+ and the manganese complex [(14‐TMC)Mn]2+, where 12‐TMC and 14‐TMC are 12‐ and 14‐membered macrocyclic ligands, 12‐TMC=1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane and 14‐TMC=1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane, is studied by means of DFT methods. B3LYP calculations including long‐range corrections and solvent effects are performed to elucidate the mechanism. The potential energy surfaces (PESs) compatible with different electronic states of the reactants have been analyzed. The calculations confirm a two‐step reaction, with a first rate‐determining bimolecular step and predict the exothermic character of the global process. The relative stability of the products and the reverse barrier are in line with the fact that no reverse reaction is experimentally observed. An intermediate with a μ‐η1:η1‐O2 coordination and two transition states are identified on the triplet PES, slightly below the corresponding stationary points of the quintet PES, suggesting an intersystem crossing before the first transition state. The calculated activation parameters and the relative energies of the two transition sates and the products are in very good agreement with the experimental data. The calculations suggest that a superoxide anion is transferred during the reaction. 相似文献
15.
Dicopper(II) Anthraquinophanes as Multielectron Reservoirs for Oxidation and Reduction: A Joint Experimental and Theoretical Study
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Dr. María Castellano Dr. Wdeson P. Barros Alvaro Acosta Prof. Dr. Miguel Julve Prof. Dr. Francesc Lloret Dr. Yanling Li Dr. Yves Journaux Prof. Dr. Giovanni De Munno Dr. Donatella Armentano Dr. Rafael Ruiz‐García Dr. Joan Cano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):13965-13975
Two new dinuclear copper(II) metallacyclophanes with 1,4‐disubstituted 9,10‐anthraquinonebis(oxamate) bridging ligands are reported that can reversibly take and release electrons at the redox‐active ligand and metal sites, respectively, to give the corresponding mono‐ and bis(semiquinonate and/or catecholate) CuII2 species and mixed‐valent CuII/CuIII and high‐valent CuIII2 ones. Density functional calculations allow us to give further insights on the dual ligand‐ and metal‐based character of the redox processes in this novel family of antiferromagnetically coupled di‐ copper(II) anthraquinophanes. This unique ability for charge storage could be the basis for the development of new kinds of molecular spintronic devices, referred to as molecular magnetic capacitors (MMCs). 相似文献
16.
Mohammad ElEzzi Romaric Lenk David Madec Jean‐Marc Sotiropoulos Sonia Mallet‐Ladeira Annie Castel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(3):819-822
The efficiency of the deprotonated aryl bis‐sulfone [2,6‐{(p‐tolyl)SO2}2C6H3]− as an O,C,O‐coordinating pincer‐type ligand was described. The bis‐sulfone precursor was synthesized using a straightforward palladium‐catalyzed cross‐coupling reaction. As a result of directed ortho metalation (DoM) through sulfonyl groups, a selective lithiation of the aryl group was achieved and the corresponding carbanion was isolated and its structure determined by single‐crystal X‐ray diffraction analysis. A heteroleptic tin(II) complex has been prepared by a nucleophilic substitution reaction. Crystallographic analysis and DFT calculations indicate that the bis‐sulfonyl moiety acts as a new O,C,O‐coordinating pincer‐type ligand with intramolecular SO coordination to a tin(II) center. The cis form with the two nonbonded oxygen atoms of the sulfonyl groups on the same side is preferentially obtained. 相似文献
17.
Janaina Marinas Pérez Dr. Holger Helten Dr. Gregor Schnakenburg Prof. Dr. Rainer Streubel 《化学:亚洲杂志》2011,6(6):1539-1545
Treatment of oxaphosphirane complex 1 , triflic acid (TfOH), and various aldehydes yielded 1,3,4‐dioxaphospholane complexes 5a , b – 7a , b after deprotonation with NEt3. In addition to NMR spectroscopy, IR spectroscopy, and MS data, the X‐ray structures of complexes 5a and 7a were determined. 31P NMR spectroscopic monitoring and DFT calculations provided insight into the reaction course and revealed the transient TfOH 1,3,4‐dioxaphospholanium association complex TfOH‐ 5a , b and/or TfOH‐ 5a , b′ as key reactive intermediates. Furthermore, it was observed that the five‐membered ring system was cleaved upon warming and yielded side‐on (E,Z)‐methylenephosphonium complexes 8a , b if deprotonation did not occur at low temperature. Overall, a novel temperature‐ and acid‐dependent construction and deconstruction process of the 1,3,4‐dioxaphospholane ring system is described. 相似文献
18.
Chin‐Ping Yang Yu‐Yang Su Kuen‐Lin Wu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5424-5438
A novel, fluorinated diamine monomer, 2,5‐bis(4‐amino‐2‐ trifluoromethylphenoxy)‐tert‐butylbenzene ( II ) was synthesized through the nucleophilic substitution reaction of tert‐butylhydroquinone (t‐BHQ) and 2‐chloro‐5‐nitrobenzotrifluoride in the presence of potassium carbonate to yield the intermediate dinitro compound I , followed by catalytic reduction with hydrazine and Pd/C to afford diamine II . A series of fluorinated polyimides V were prepared from II with various aromatic dianhydrides ( III a–f ) via the thermal imidization of poly(amic acid). Most of V a–f could be soluble in amide‐type solvents and even in less polar solvents. These polyimide films showed tensile strengths up to 106 MPa, elongation at break up to 21%, and initial modulus up to 2.1 GPa. The glass‐transition temperature of V was recorded at 245–304 °C, the 10% weight loss temperatures were above 488 °C, and left more than 41% residue even at 800 °C in nitrogen. Low dielectric constants, low moisture absorptions, and higher and light‐colored transmittances were also observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5424–5438, 2004 相似文献
19.
A novel method for the preparation of chromogenic calixarenes with azo groups was reported.p-Substituted(-NO2,-CH3,-Cl)amilines were diazotized with isoamyl nitrite in EtONa/EtOH under refluxing condition.Fifteen mono-,bis-,tris-and tetrakis(p-substituted phenyl)azo calix[4]arenes (including proximal and distal isomers) were obtainged respectively by diazo-coupling in different molar ratio to calix[4]arenes(1) under pH=7.5-9.0 in non-aqueous solution at 0-5℃.^1H NMR and ^13C NMR spectra of (p-substtituted phenyl)azo calix[4]-arenes indicated that they existed in cone conformation in solution. 相似文献
20.
以4-硝基对苯腈,氨水和铜盐反应于在原位水热条件下合成了二(2,4-二(对硝基苯)-1,3,5-环戊二烯铜配合物,通过单晶X射线衍射,元素分析,红外,核磁光谱和热重分析等手段对其进行了表征。结构分析表明,铜与四个源自原位合成的配体上的氮原子配位形成平面四边形构型。基于密度泛函的理论计算对配合物的热力学稳定性进行了阐释。 相似文献